Leon letrange



(No Model.

L. LETRANGE.

PROCESS OF AND APPARATUS FOR REDUCING ZINC ORES.

Patented Oct. 9 1883.

WITNESSES:

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LEON LETRANGE, OF PARIS, FRANCE.

PROCESS OF AND APPAFATUS FOR REDUCING ZENC ORES.

SPECIFICATION forming part of Letters Patent No. 286,208, dated October 9, 1883. Application filed September 13, 1891. (No model.) Patented in France June 21, 1861, No. 143,519; in Germany July 8, its], No. 21,775; in Belgium July 16, [$81, No. 55,137,- in England July 22, 1881, No. 3,211; in Italy August 10, 1881, No.13,-B; in Sweden October 5, 1881; in Portugal October 1!), 1881, No. 701, and in Austria-Hungary November 12, 1881, No. 26,461.

To rtZZ whom it may concern Be it known that I, LEON LETRANG'E, a citizen of the French Republic, residing in Paris, France, have invented certain Improvements in Processes of and Apparatus for Reducing Zinc Ores; and I do hereby declare that the following is a full and exact description of the invention.

I will first describe the process.

The purpose of the invention is to reduce zinc ores economically by the wet process, using only heat for a slight or very moderate roasting of the orcs preliminary to the main process. In addition to the production of me tallic zinc in a pure state, a considerable quantity of sulphuric acid is obtained. Zinc ores are generally of two kindsblendc, or the sulphuret, and calamine, or the carbonate,of zinc. In the dry process of reducing these ores blende is roasted for the purpose of entirely expelling the sulphur and reducing the ore to oxide of zinc. The sulphur is all carried off in fumes, and is not only lost, but is very injurious to surrounding vegetation and animal life. Galamine is also roasted to expel the carbonic acid and reduce the ore to an oxide. The oxide of zinc is then subjected to a high degree of heat for a long time in closed vessels, whereby about four-fifths or five-sixths of the metallic zinc in the ore is obtained, and this in an impure or alloyed state. The process is very expensive, consuming double the weight of coal compared with the weight of the ore itself, and requiring skilled and costly labor.

By the wet process as improved by me, the zinc is produced quite pure. Very little heat is required. Sulphuric acid is also obtained as a commercial product, and associated metals such as lead, silver, and copper-are readily separated and saved.

I will first describe the entire process, and then distinguish what is of my own invention.

The process is begun with blende, or a sulphuret of zinc. It is first roasted with a very moderate heat-never allowed to become excessive. This mode of roasting, instead of expelling all the sulphur, merely vaporizes the excess of sulphur, which will leave the ore in the state of a sulphate, which is soluble in wa ter. Very little fuel is consumed in this roast ing. For the purpose of economy in utilizing the sulphur which is expelled from the blendc, a quantity of calamine is also roasted at the same time as the blende. This may be placed in the same roasting-oven as the blende, or in another oven or passage, into or through which the sulphunvapors from the roasting blcndc pass, and thus attack the calamine ore, from which the carbon is expelled, and convert it into a sulphate also. The quantity of calamine is to be suiiicient to unite with the sulphurvapors which come to it and form the required sulphate. If more calamine is at hand to be reduced than the blendc will furnish sulphur for, sulphuric acid isadded sufficient to convert the oxide of zinc obtained by the roasting of the calamine into a sulphate of zinc, to be subsequently reduced in the wet way. This acid is obtained as a final result of the pro cess-ordinarily much more than enough to serve for this purpose-and thus no extrinsic acid is required.

The sulphate of zinc having been obtained from the two ores together, as above described, the wet or main process will now be described in connection with the description of the ap paratus used. It may be here premised that the process includes the final deposition of the metal from the sulphate of zinc by a current of electricity upon zinc plates, or plates of other metals, -from which the deposited metal may be readily stripped, and the recovery of the sulphuric acid thereby set free from the bath.

The apparatus consists, essentially, of a series of vessels, in which the zinciferous substance is transformed into a sulphate of zinc; a motive power, which may be steam, water, or horse power; a Grammc machine, or any electrical machine capable of producing electricity by means of a motor; and a vessel .or series of vessels in which to precipitate the metallic zinc by means of a current of electricity.

The apparatus is substantially represented in the acconnpanyingdrawings, of which Figure 1 is a sectional elevation of the apparatus.

Fig. 2 is a plan; and Figs. 3 and 4 are illustrative diagrams, which will be referred to hereinafter.

A A A A are reservoirs or vessels, preferably set in masonry and coated interiorly with bitumen or some similar substance to render them perfectly tight. These vessels are connected by means of pipes a a a a, which lead the liquid from near the bottom of one vessel to the top of that adjacent,wherein the liquid stands at a little lower level. There may be any number of these connected reservoirs, either placed in a circle, as shown in Fig. 3, or side by-side, as shown in Fig. 4.

The four reservoirs being filled with the mineral, I letfiow into the first vessel,A, dilute sulphuric acid, which dissolves the oxide of zinc therein and converts it into sulphate solution. The excess of liquid then passes on successively to the other vessels, A A A", converting the zinc and dissolving out the sulphate, until the solution becomes saturated.

By this time the oxide of zinc in the first ves sel,A, is entirely converted, and the communication between it and the vessel A is cut off and the saturated sulphate solution in A drained oif into asuitable reservoir, B, through one of the pipes a c,which connect all of said vessels with said reservoir, as shown in Fig. 2. The vessel A is now cleaned of the residuum and refilled with mineral, and while this is being done the acidulated liquid is allowed to flow into vessel A, in which the material is treated in precisely the same way as that in the vessel A was treated, as described. Thus each vessel in succession is filled with mineral, acidnlated, drained, and refilled successively. The acidulated liquid may be supplied from an elevated reservoir, It, through a pipe, a, as shown. The saturated solution of sulphate of zinc collected in the reservoir B may be filtered and purified by well-known means, so that the resultants of precipitation may be pure; but it is not absolutely essential. The residuum taken from the vessels A A A A may be submitted to special treatment for the recovery of the lead and silver which will usually be found in it.

C O are the reservoirs or vessels in which the metallic zinc is precipitated from the sulphate solution by means of electricity. These are by preference made of wood, and lined with glass, lead, or other material which will resist the action of sulphuric acid. In these vessels are placed a series of thin plates of zinc, b b, which serve as cathodes on which the zinc is precipitated. The superfieies of these should be proportionate to the decomposing-power of the electric current employed to obtain the best results; or the cathodes maybe of copper or polished brass, from which the zinc deposit will readily detach itself. Op-

' posite to each cathode is placed an anode, c,

of carbon or other conducting material, of an insoluble nature, or a conducting material covered with a coating which is insoluble in the acid. The solution of sulphate of zinc is con. ducted by the depending pipes (l d to the bottom of the vessels O O in a manner capable of regulation as to the desired quantity, and this may be effected by stopcocks in the pipes d d. The zinc precipitated on the cathodes by the decomposition of the sulphate liberates a proportionate quantity of sulphuric acid, which, being lighter than the saturated solution of sul phate, rises to the top of the bath. This acid is ledoif as fast as formed by means of pipeso 0, which tap the vessels at the level of the sulphate solution and discharge into areservoir,D. The

solution is fed to the baths to replace the zinc as it is precipitated and removed, and by this means the level of the solution in the bath is maintained at all times nearly the same. The degree of concentration and acidity of thebath is also maintained constant. reservoir 1), or so. much of it as is necessary to convert the oxide of zinc into sulphate,is drawn from the said reservoir through suitable pipes into the reservoir It, from which it can be drawn as fast as wanted into the vessels A A A A".

Snlphuret ores have been roasted in such a manner as to produce soluble sulphates, wholly or in part, and carbonates have been roasted for converting the ores into oxides. I am not aware, however, that sulphurets and carbon ates have been roasted simultaneously in the same or communicating chambers in such a manner that the sulphur given off from the sulphurets to form sulphates shall unite with oxides produced by the roasting of the carbonates, so as to convert both ores at once into sulphates, as in my invention.

I am also aware that pure metals have been precipitated from sulphates in solution by electric currents; but I am not aware that metallic ores on the large scale have been first reduced to sulphates in solution, and the pure metal deposited. therefrom by electric cur rents on metallic plates, and the sulphuric acid set free in the same operation, separated, and saved in economic quantities for commercial use.

\Vhat I claim, therefore, as my invention, and desire to secure by Letters Patent, is-

1. In reducing zinc ores, the process of con verting them into soluble sulphates, which consists in roasting the snlphuret ores of zinc and the carbonate ores of zincsimultaneously in the same or communicating chambers and producing a sulphate from the carbonate ores with the sulphur thrown off from the snlphuret ores in reducing the same to a sulphate, substantially as and for the purpose herein specified.

2. The process of reducing zinc ores and producing pure metallic zinc and sulphuric acid simultaneously therefrom,whieh consists in si-. multaneously roasting snlphuret ores and carbonate ores in the same or communicating The acid in the chambers, and thereby converting both ores 1 0 into soluble sulphates, then leaching these roasted ores, and then depositing the metallic seems I 3 zinc from a solution of the sulphates by electric currents on metallic plates, and drawing sulp hurie acid at the same time from the solution as fast as set free by the Sold electric currents, substantially as and for the purpose herein specified.

3. In an apparatus employed in the reduction of zinc ores, as herein described, the coin bi nation of the series of digesting-vessels A A A" A, the reservoir B, the eleetric depositing vessel or vessels 0 (J, and pipes connecting the vessels and reservoir, substantially as and for the purpose herein-specified.

'lhe'combination of the series of digesting-vessels A A A A, the reservoir B, the

electric depositing vessel or vessels 0 U, the

acid-reservoirs I) R, and pipes connecting the said vessels and reservoirs, substantially as herein specified. I

5. The apparatus for use in the process of reducing zinc ores,whieh consists, essentially, in a reservoir for the sulphate solution, a precipitating-vessel provided with suitable an odes and cathodes, a pipe provided with a regulatiiigcock, leading from the reservoir to near the bottom of the preeipitating-vessel, and an outlet-pipe for the freed acid, arranged in the said vessel at the desired level of the liquid therein, whereby the strength and quantity of the sulphate solution in the )recipitating-vessel are maintained constant, substantially-as herein specified.

6. The apparatus for use in the process of reducing the ores of zinc, which consists in an acid-reservoir, R, dissolving-tank with compartnients A A A A, pipes a, a, and a reservoir B for the sulphate solution, precipitat- Vitnesses:

Row. M. Hoornn, CHARLES lvLxnsniiiuip. 

